1. Field of the Invention
This invention pertains to improvements in center feed material grinding mills having a closed bottom and an opposite side outlet for ground material.
2. Description of the Prior Art
Pertinent prior art is represented by Lykken et al U.S. Pat. No. 2,931,581 of Apr. 5, 1960 in which a rotary grinder is fed with material to be ground and air at the same side of the rotor, and in which the rotor acts as a fan for propelling the fine material as a result of the grinding in an upward direction aided by the lifting of incoming air. The grinder is provided with a classifier vertically above the grinder rotor with provision for returning heavier and oversize material back to the chamber for further grinding. The return of the heavier and oversize material is determined by gravity separation from the classifier.
A further example of the prior art is represented by Knoblock U.S. Pat. No. 1,104,121 of July 21, 1914 wherein a rotor is fed with material on one side of a grinding chamber and air is circulated by fan at a circumferentially spaced position of the grinding chamber so that the material ground by the rotor is propelled upwardly in a classifying chamber which has spaced outlets for capturing the ground material depending on its size and the distance that the material is thrown up in the chamber. A further example of the prior art is represented by Japanese Pat. No. 36-4084 of Feb. 27, 1936, and in which the arrangement of the operating parts and the housing structure is somewhat similar to the disclosure in Lykken et al.
Patents of lesser pertinence are Williams U.S. Pat. No. 3,794,251 of Feb. 26, 1974, and U.S. Pat. No. 3,826,208 of July 30, 1974. In these patents the grinding chamber has a closed bottom and a center feed through a venturi throat with the air supply located below the throat and above the grinding chamber.